Recently, as oil prices rapidly increase, researches are being actively conducted on a hybrid construction machine which improves fuel efficiency by storing surplus power of an engine in electric energy storage devices such as batteries, ultra capacitors, or the like and supplying power from the electric energy storage apparatus to the engine having insufficient power. The hybrid construction machine such as an excavator includes an oil hydraulic pump which hydraulically drives work elements such as a boom, an arm, a bucket, and the like, and an engine assistant motor is connected to the engine for driving the oil hydraulic pump. The engine assistant motor assists a drive of the engine, and charges electric energy by power generation in the electric energy storage device. In addition, a turning control apparatus is being developed which turns an upper turning body using a turning motor which is driven by electric energy of the electric energy storage device.
In the hybrid construction machine in the related art, the oil hydraulic pump is driven by the engine and the engine assistant motor, surplus power of the engine and regenerative energy of the engine assistant motor are converted into electric energy and stored in the electric energy storage device, and the engine assistant motor stores electric energy in the electric energy storage device or is driven by electric energy stored in the electric energy storage device. The turning motor, which drives the upper turning body, is driven by electric energy, and electric energy between the electric energy storage device and the engine assistant motor, or between the electric energy storage device and the turning motor is converted by an power converter and used. Here, the constituent components are connected to the power converter, and operations thereof are controlled by a hybrid control unit (HCU).
However, in the aforementioned hybrid construction machine in the related art, electric power is supplied from a typical battery, which is provided in a vehicle separately from the electric energy storage device, to the hybrid control unit in order to supply electricity for starting the engine of the vehicle or supply electricity to various electronic devices. That is, electric energy is supplied from the battery to a switching mode power supply (hereinafter referred to as SMPS) by a switch Key1 which is operated by a key on signal by an operator, and the SMPS controls the supplied electric power and supplies electric power to the hybrid control unit.
Meanwhile, when a turning drive of the upper turning body is performed using the turning motor, a drive direction and a drive speed of the turning motor are controlled in accordance with a signal transmitted from the hybrid control unit. For this reason, when electric power of the battery, which supplies electric power to the hybrid control unit that controls the turning motor, is blocked, that is, when the switch Key1 is off by a stop of the engine or a key off manipulation of a driver, a control operation of the hybrid control unit is stopped, it is impossible for the turning motor to be controlled such that the upper turning body continues the turning operation for a predetermined time.
When it is impossible to control the turning operation of the upper turning body as the stop of the engine or the key off manipulation of the driver is performed during the turning operation as described above, rotational inertia of the upper turning body is high, and therefore there is a problem in that when the upper turning body collides with surrounding obstacles or the like within a turning radius, or a front collides with the ground on a hill or the like, the vehicle, equipment, and the like are damaged, or injury to a human is caused.
The discussion above is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter.